In the past, impoundment ponds for fluids have been constructed using layers of plastic for lining the surface of an excavation in the earth which are usually then covered with a layer of clay to maintain the plastic in a uniform condition, exclude air bubbles and to protect it from tears and the like. In my application Ser. No. 252,676, I disclose a vertical cut-off system that assures absolute water tightness wherein a pair of plastic films are used to line a slurry trench and a pervious layer fills the space between the two plastic layers to act as a filter. Draining of the filter material is used as a method of maintaining the effectiveness of the barrier and with a minimum amount of pumping at intervals guaranteeing that any pollutant which crosses the initial barrier is collected and eliminated. The object of the present invention is to extend that plastic, pervious layer and pump-plastic layer technique to large impoundment ponds without the use of slurry walls. According to this invention, an impoundment pond is constructed in the usual fashion by excavating the impoundment pond space in the earth and lining same with a layer first layer of plastic. Thereafter, according to the present invention, a system of self-starting pumps are placed in collecting pipes at uniform intervals along the slope of the impoundment walls or surfaces. These pipes are of such a diameter as to receive conventional self-starting pumps e.g. pumps which sense the presence of a fluid and automatically begin pumping the fluid when it reaches a predetermined level. The pipes are covered with a pervious layer such as sand and then an inner layer of plastic, which in the preferred embodiment, is significantly thicker than the outer layer is applied over the pervious layer and then the conventional cap or layer of clay is applied thereover. The outer ends of the two plastic layers may be sealed or otherwise covered with a clay cap so as to prevent the draining of surface water thereinto.